Decimal to Hexadecimal Conversion

#include<stdio.h>
#include<conio.h>
#include<math.h>

void main()
{
 long int num;
 clrscr();

 printf("Enter the decimal number : ");
 scanf("%ld",&num);
 
 long int rem[50],i=0,length=0;

 while(num>0)
 {
  rem[i]=num%16;
  num=num/16;
  i++;
  length++;
 }

 printf("Hexadecimal number : ");
 for(i=length-1;i>=0;i--)
 {
  switch(rem[i])
  {
   case 10:
   printf("A");
   break;
   case 11:
   printf("B");
   break;
   case 12:
   printf("C");
   break;
   case 13:
   printf("D");
   break;
   case 14:
   printf("E");
   break;
   case 15:
   printf("F");
   break;
   default :
   printf("%ld",rem[i]);
  }
 }

 getch();
}

/*
Summary: Converts decimal number which is base 10 number system 0-9 to hexadecimal which uses the digits from 0 to 9 and A, B, C, D, E, F..
*/